Testing AIS MOB beacons, ACR's DSC feature especially

... written for Panbo by Ben Ellison and posted on Aug 25, 2017

testing_four_AIS_MOB_beacons_cPanbo.jpgGiven my accidental activation of an AIS MOB beacon a few weeks ago, it seemed like a good time to test beacons again. I hoped to at least see all the major brand multifunction displays properly react to an AIS MOB test transmission, putting up the distinct safety message that I should have seen during "the incident" and that every owner of an AIS MOB should be familiar with. Potential beacon users should also understand the specific activation, test, and deactivation controls on their device, plus I have two newer beacons with special features worth examining in detail...

To recap some AIS MOB beacon history, I first discussed the McMurdo S10 and Kannad R10 pictured above in early 2011. Back then they were often called personal AIS SARTs -- the term I used when I first tested the WeatherDock EasyRescue A040 -- but now they are usually called personal AIS beacons, or simply AIS MOB beacons, to distinguish them better from larger commercial-grade AIS SARTs. And some prefer "devices" or "locators" to "beacons" to also distinguish these AIS MOB handhelds from Personal Locator Beacons (PLBs).

At any rate, AIS MOB beacons have proven themselves effective, able to alert your boat that you're overboard and then provide realtime position information to guide a retrieval. Nearby vessels may also see the special "AIS MOB ACTIVE" safety message highlighted on their screens and may come to the rescue or notify the SAR professionals (as I accidentally verified in late July). But it's imperative to know how your boat's electronics will react to an AIS MOB transmission because self-rescue is the primary goal and not all AIS display devices do it right yet. Plus, it's also important to know how to activate the device manually before you find yourself trying to figure it out in desperate circumstances, even if it's supposed to activate automatically.

Before I get into activation and test details -- plus the very interesting secondary VHF DSC alarm provided with the ACR AISLink -- I highly recommend a look at Pip Hare's AIS MOB testing article for Yacht World in the UK. Hare was able to activate numerous beacons -- not just try the short test function -- and thus can testify to how well they all performed. She also breaks down the differentiating details well, and included in her testing were the McMurdo S10 above, as well as the popular Smartfind S20 (which is just like the no-longer-available Kannad R10).

The S10 is usually worn on a belt and can only be manually activated (and it's the only AIS MOB beacon I know of with a magnetic switch possibly subject to weird outside magnetism). But the S10/R10 can be set up to automatically activate with help from an inflatable lifejacket, like several other designs including the new AISLink.

ACR_AISLink_MOB_mount_detail_cPanbo.jpgThis photo shows all the bits and pieces that come with the ACR AISLink MOB, though you'll only use some of them depending on the lifejacket. For instance, that lower gray clip might secure the beacon to a sturdy oral inflation tube, while the (very) sticky reflector tape secures the end of the activation tether so that automatic inflation pressure makes thing happen. There's lots of details to such a setup and the results, but fortunately ACR produced an excellent video covering both.

Even if you don't go for an automatic lifejacket install, I think it's a good idea to activate (and quickly turn off) the AISLink anyway. Familiarity with rarely-if-ever-used safety gear is key to success. Also, in my experience, the AIS MOB test message you should try is apt to work better if the antenna is deployed (though the manufacturers don't usually ask for that).

ACR AISLink antenna reset.jpgIn this photo I'm using the supplied tool to rewind the AISLink's antenna before sliding the activation door back in place. Everything here seems very well designed and manufactured; in fact, it reminded me of Ocean Signal gear I've handled, like the RescueMe PBL1, and that's no surprise, as I'm fairly certain that the Ocean Signal team that already developed the AIS MOB1 had a lot to do with creating the AISLink for sister brand ACR. And, incidentally, it's interesting to think about how ACR and Ocean Signal lifejacket electronics may evolve now that the ACR conglomerate has acquired the UK inflator manufacturer United Moulders.

Weatherdock_EasyOne_AIS_MOB_antenna_reset_cPanbo.jpgNow I've never tested automatic AIS MOB activation by inflation, but I'll guess that there are many ways it can go wrong in the real world. For instance, activation sliders have to slide just so to effectively depress an ON button on the way, and even well sprung antennas don't always spring the way they're meant to. And that's why it's noteworthy that the Weatherdock EasyOne AIS MOB uses completely different auto activation technologies. Note the water-soluable white pill sitting in that antenna lock. When it dissolves the antenna uncoils forcefully, and then it's a pair of water contacts that actually activate the beacon. It's also easy, almost too easy, to deploy the antenna by pulling off the clear face plate and then the ON switch is exposed if the water activation isn't working.

But I will also note that the EasyOne antenna deployment caused the rewind tip to fly free, and I could not have done the rewind above without using superglue to reattach the tip. I'm also personally skeptical about the chances of a person overboard who is unable to manually activate a beacon that fails to do so automatically, but if that's a high priority EasyOne may be the one.

AIS MOB test screens

Simrad_NSS_evo2_with_AIS_MOB_test_cPanbo.jpgBack in 2012 few AIS displays properly displayed AIS MOB test messages, then I got to write about how thoroughly Garmin nailed it, and now I can report that all four major brands seem to have good AIS MOB routines built into their MFD operating systems. That's Simrad NSS evo2 doing the job above; note the clear alert about what's happening along with three choices of how to handle this special AIS message. Though "SART" is somewhat old terminology, this is just what you'd want to see when a real AIS MOB/SART is activated and that's the point of the test mode . (Also note the terrific Audio and Autopilot sidebars that just arrived with evo2 NOS 57 update.)

Furuno_TZT2_with_AIS_MOB_test_cPanbo.jpgFuruno does things a little differently. Rather than a pop-up safety message the TZT2 display flashes that "AIS SART Alarm" at the top of the screen, accompanied by an audio alarm if enabled. Like the other MFD chart/AIS displays, the TZT2 overlays the unique AIS MOB target icon, and if you click on that you get the safety message detail and the chance to make the AIS MOB/SART location into a go-to waypoint.

Garmin_7612_AIS_MOB_test_result_cPanbo.jpgGarmin's clear response to an AIS MOB test was no surprise. In fact, their MFD interface was anticipating similar AIS EPIRB tests back in 2012 and McMurdo just recently introduced the first AIS EPIRB.

Raymarine_LightHouse_2_and_3_AIS_MOB_test_cPanbo.jpgThese days older Raymarine MFDs run LightHouse 2 and Axiom MFDs run LH 3 with lots of changes coming, but that doesn't matter in terms of AIS MOB beacons because both versions handle them fine.

AIS_MOB_beacon_test_with_Em-Trak_B400_n_Vesper_XB8000.jpgAnd it's no surprise that dedicated AIS target displays like the Vesper WatchMate app and the Em-Trak B400 display AIS MOB tests very well. So what AIS displays failed the MOB test test? Neither the ICOM M605 VHF with AIS receiver nor the Simrad RS35 with AIS rx noticed that the AIS MOB test messages with their unique "972xxxxxx" MMSI and attached "MOB TEST" safety message were anything different than a regular AIS target (that would appear at your vessel's stern and then appear to fall away as you perhaps carried on unaware).

I'm not aware of any VHF radio with AIS reception that understands AIS MOB beacons yet and, while I'd love to be corrected, that's disappointing. {Update: the Standard Horizon Matrix GX2200, and probably other SH VHF/AIS radios, handle AIS MOB beacons well; see comments below.} But Icom has already expressed an interest in updating their AIS rx radios, and it's true that both the M605 and the RS35 passed the AIS MOB test info to all the MFDs above just fine. But wouldn't it be nice, especially on offshore sailboats, if you could leave the MFD off and count on your VHF to help with an AIS MOB?

So there are still good reasons beyond familiarity to run AIS MOB tests using your boat's electronics. And let me add here that some of my tests did not work even though I usually had the AIS MOB beacon antenna deployed. For instance 2 or 3 MFDs on one NMEA 2000 network with a common AIS source would typically see the test signal and then a second test would work with a different 2 of 3. I think it's just because of the very short test sequence (which you may have to run again), but note that a real AIS MOB ACTIVE mode transmits 8 times per minute for 24 hours minimum. Also note that Panbot Allan Seymour saw one of my AIS MOB tests from Sally W out in the Bay past lots of moored boats and land about 2.5nm away.

AIS MOB DSC!

ACR_AISLink_MOB_MMSI_Programmintg_web_app_cPanbo.jpgSo one reason to get an AIS MOB beacon with a secondary DSC alert is because your VHF with AIS receiver probably won't alert you about the primary AIS MOB message. But there are other good reasons: The audio distress alert on your VHF is probably quite loud and effective; you may sometimes have your radio on when your regular (or other) AIS displays are not powered up; and the DSC alarm may fetch boats in your area that don't even have AIS (though that depends on your region, to be explained below).

But how do you program your boat's MMSI into a waterproof handheld safety device with no normal ports? Well, as illustrated above, you type your MMSI into an ACR configuration program and then hold the AISLink up to a flashing screen that talks to an optical sensor that's apparently integrated with the beacon's LED strobe. It is one of the oddest electronics configurations I've ever done, but it worked fine. In fact, I used the alternate web app on my iPad, instead of the PC program, and I imagine a smartphone would work well, too. (It may take more than one try because holding the beacon and the little light-focusing accessory is a bit awkward.)

It's also possible to test the DSC feature, but before discussing that, let's have a look at what an AIS MOB DSC alert means in different parts of the world.

AIS only: Canada, France, Denmark, Latvia
AIS + DSC Individual Distress Relay call plus group call sent after 30 minutes: USA
AIS + DSC Individual Distress Relay call only: Germany, Netherlands, United Kingdom
AIS + DSC Individual Distress Relay, All Ships Distress Alert (manual initiation): All other European countries
AIS + DSC Individual Distress Relay, All Ships Distress Alert, sent once on AISLink MOB activation and on manual initiation: Rest of the World.

The list above can be found online in the ACR AISLink MOB FAQ, and also in the Ocean Signal MOB1 FAQ (they are virtually the same). This is valuable information as standards for MOB DSC alerts are obviously not global (and not easily found either). As you can see in the list, some countries like Canada and France don't allow it all. But everywhere else, an AIS MOB beacon with DSC should be able to set off a DSC Individual Distress Relay alert with the source position on the mother vessel's VHF. There's a significant caveat about that below, but further note that in U.S. waters, the beacon can also send out a DSC group call after 30 minutes and in many areas the person overboard can manually initiate an all ships distress alert, often in addition to a single automatic all ships call on beacon activation.

Yes, this sounds messy, but at least ACR and Ocean Signal have made the programming easy. When you go to either site to download the PC configuration program or link to the web app, the site identifies which DSC alert zone you're in and only offers you the appropriate options.That's why I could program individual and group MMSI's in the U.S.

ACR_AISLink_MOB_DSC_call_on_Icom_M605_n_SH_HX851_cPanbo.jpgUnlike an AIS MOB Test, which is globally regulated and closely related to an actual AIS MOB ACTIVE alert, an MOB DSC test is treated as a routine individual DSC call. In other words, you will not hear the loud alarm associated with a DSC Distress call. In fact -- here's the caveat I mentioned -- you won't know for sure that your radio will respond loudly to the DSC Individual Distress Relay call because the Class D VHF radios typically found on yachts are apparently not mandated to support this function (like Class A's are).

Listed on the ACR and OS FAQ pages are numerous Icom radios that are known to handle a DSC Individual Distress Relay call properly, as well as one each from Simrad and Standard Horizon. I suspect that there are many more, but obviously it would be great if all VHF manufacturers participated in this testing and also made sure to include the feature in future models. Of course it will help if the VHF folks get bugged by boaters who already own AIS MOB DSC beacons or are considering the purchase.

And despite the standards messiness and VHF uncertainties, I'd sure consider the fairly small extra cost of an AIS MOB beacon with DSC. But hopefully I've made the point that whatever safety devices you have, it's a good idea to get familiar with how they work and to test them as far as possible (without causing an incident ;-).

Finally, while I was at it, I also checked the various PLBs I've been long testing and was again particularly impressed with ACR AquaLink View. Its size and cost are bigger than other perfectly good PLBs, but it sure is nice to have that little display scroll through specific test results, like showing its GPS locate my position in seconds and that the PLB still had at least 24 hours of battery left, even though it should have been replaced by 5/2016. (By the way, the COSPAS-SARSAT registration for this PLB -- handled by NOAA in the U.S. -- is up-to-date, though I should have replaced the sticker.)

ACR_AquaLink_tests_fine_after_battery_expiration_cPanbo.jpg

Comments

Curious, if you name the MMSI of a AIS MOB in you MFD, say "Walter's MOB" what would the MFD show during an alert or test.

Posted by: Walter at August 26, 2017 11:42 AM | Reply

Hi Walter, I doubt that the AIS MOB alert would change, but maybe the MOB icon would get the "buddy" if your MFD has that feature. I'll give it a try (and also meant to see how PC Charting programs like Coastal Explorer and TimeZero handle an MOB test.

Incicdently, there are dedicated AIS MOB alarms that let you name the beacons on your boat, both from Ocean Signal and Digital Yacht, I think.

Posted by: Ben in reply to Walter at August 26, 2017 12:40 PM | Reply

Let me say up front I really like the AIS MOB device concept. In fact, I purchased the ACR AISLink last spring to put in my new Spinlock PFD. This started me down the road to some minor disappointments. First, The AISLink didn’t fit in the Spinlock so I felt I had wasted money when the intention was to have this deploy automatically while stored inside my new PFD. But just for the hell of it I tried installing it in the old Mustang Hydro-static PFD, the one I keep onboard for crew, and it fit just fine. ACR AISLink is just a hair too big for the Spinlock. This left me without an AIS MOB so I purchased the Ocean Signal and it fit inside the Spinlock perfectly.

Like Ben did, I laid out all the little pieces that came with the device and read the instructions. My first impression, “This is a first generation, almost primitive way to do what I know will change down the road”. Why can’t the AIS MOB manufacturers pick up the phone and call the PFD guys and talk about a standardized way to quickly and securely install an AIS MOB in any PFD? Come on ACR, Spinlock, Mustang!

When you look at the picture in Ben’s post it’s a collection of cheap string, plastic doodads with tape and ribbon. I was hoping for something more positive then leaving the integration of the AIS MOB product with PFD up to me to figure out. After the install I can say “I think” I might have it right, but only a MOB situation will prove if it will deploy as it should. Not that the device is the issue here. If it fails to deploy it will be all my fault for not getting the plastic pieces snapped together properly or the black ribbon wound around the bladder in the right direction or the string - I think the string is still on my desk.

So, if you see what I mean, cooperation between PFD and AIS MOB manufacturers could make this installation a fool proof, drop it in the pocket and clip to the bladder and you’re done, type of simple, foolproof confidence building experience.

I won’t even get into the “flashing light on the computer screen” programing routine. Didn’t they ever consider using a micro USB port? Well I’m not a computer tech so maybe there is a good reason why easier programing methods were not used here.

I’m happy I bought the two devices, no regrets, I think they will work, but I just see lots of room for improvement when it comes to having the end user fold it into a PFD.

Posted by: Richard C at August 26, 2017 4:44 PM | Reply

Thanks, Richard, great points except I disagree about the optical programming. It might be unfamiliar, but it was just as easy as a wired connection, I thought, and a lot more waterproof.

I notice that Spinlock sells a deck vest already fitted with an MOB1 and also has video about how to do the install:

https://www.spinlock.co.uk/en/categories/lifejackets/product_groups/ais-mob1

Posted by: Ben in reply to Richard C at August 28, 2017 9:24 AM | Reply

Ben,

I see your point on the optical programing being waterproof, certainly a USB would not be waterproof no matter how hard they tried. This is the first time I ever came across the “optical computer screen flash” method of programing anything, but it did work for me the first try.

Yes, the MOB1 fit perfectly and this is the one I purchased after realizing the AISLink was too big for the slender design of the Spinlock Deckvest.

I did try to find a vendor that sold the Deckvest with the MOB1 pre-installed, but it seemed no one wanted to take a chance and stock this option. The local vendor I spoke to told me that his problem was aging stock. As soon as he receives his supply of Spinlock PFD’s they begin to lose value as the inflator has a replacement date. He went on to say that the Deckvest with MOB1 has few customers interested in this costly added option and therefore they may sit on his shelf a very long time depreciating in value.

So…, no inventory in the store means customers can’t buy the Deckvest with installed MOB1 and Spinlock thinks no one wants one. In my opinion, this is a good reason for Spinlock to sell direct.

Standardizing the way an AIS MOB is installed in any inflatable PFD would take the possibility of user installed error out of the equation and insure proper activation should the PFD be deployed for the real thing. Standardization would take cooperation between PFD and AIS MOB manufacturers, something only the brave would attempt.

Posted by: Richard C in reply to Ben at August 28, 2017 11:38 AM | Reply

Ben,
I can confirm that the Standard Horizon Matrix GX2200 fixed VHF works just nicely together with the Kannad R10. The alarm is loud enough and the display tells you exactly the bearing and distance to the casualty. Also the AIS SART test mode is well suported.
Cheers,
Chriggel

Posted by: chriggel at August 29, 2017 8:26 AM | Reply

Thanks, Chriggel, and kudos to Standard Horizon. Now I notice that they advertise AIS SART display right near the top of the feature list:

http://www.standardhorizon.com/indexVS.cfm?cmd=DisplayProducts&DivisionID=3&ProdCatID=83&ProdID=1769

Moreover the manual indicates that the GX2200 supports AIS MOB beacons and EPIRBs too, and the response sounds good, as you noted. I will correct my entry.

I also note that the GX2200 can receive (and send) DSC Distress Relay messages, so maximum AIS MOB beacon support from Standard Horizon. I imagine these features extend to other SH VHFs and VHF/AISrx models, but I'd check the specific manual to be sure.

Posted by: Ben at August 30, 2017 10:25 AM | Reply

I haven't yet tested our Smartfind S20 nor our Kannad R10, but just now sailing 6 miles away towards Athens, someone fired 3 tests from 970117847 (4:15pm, 4:18pm, 4:39pm, 4:46pm), with the following results:

B&G Zeus (3.0.12): Dialog on screen, 3 messages on the AIS list page. No audio alarm.

B&G Zeus2 (older software 4.5, before the current one with the Audio/Autopilot sidebars): Dialog on screen, 3 messages on the AIS list page. No audio alarm.

B&G V50 VHF with AIS ON: SART AIS Target? What's SART? Yeah, I got all the AIS targets in the area, but the MOB? Never heard of him. He can drown for all I care!

I wonder if the lack of audio alarm is by design or if I have some obscure setting off.

Posted by: Xavier Itzmann at September 7, 2017 9:56 AM | Reply

Thanks, Xavier. The MMSI starting "970" means that actually was an AIS SART (Search and Rescue Transmitter) being tested. AIS MOB devices start "972" and EPIRB-AIS beacons start "974":

https://www.navcen.uscg.gov/?pageName=mtMmsi#format

SARTs are essentially bigger, commercial versions of personal AIS beacons, meant to locate lifeboats better than the radar transponder type SARTs.

And all of them, including the new AIS EPIRBS, use AIS in the same low power local way and come preprogrammed with MMSI numbers.

Posted by: Ben in reply to Xavier Itzmann at September 7, 2017 11:27 AM | Reply

I am not sure the DSC regulation is correctly stated. I think one problem is how ot is broadcasted. Namely, do the devices only send the alert - or do they also have a receiver, which detects the acknowledgement (implying: repeated broadcast until ack, then silent)? I think the only AIS MOB which has a receiver is Weatherdocks' easyRESCUE-PRO, which is bulky and expensive. At least last time when I checked, all others only broadcasted w/o being able to receive the ack, hence, the repetition is limited and also to whom it is transmitted - and this also relates to which DSC call is permitted in a given country.

Posted by: Tobias at October 19, 2017 1:48 PM | Reply

Correct, The last ITU DSC standard report very clear that in DSC MOB operation, the MOB unit shall be receive and manage the Ack message.... in fact if the MOB have no receiver inside, is out of ITU requirement.

Posted by: daniele banfi in reply to Tobias at November 14, 2017 7:32 AM | Reply

more clarify in MOB operation in DSC , see ITU M.493-14 paragraph 16

Posted by: daniele banfi at November 14, 2017 7:37 AM | Reply

Hi Daniele,

I do not have access to ITU M.493, so if you have a link to it, that would be great.

Are you saying that devices like the ACR AISLink with limited DSC transmission (by regional authorities) and no DSC receiver are illegal? I'd be really surprised.

Posted by: Ben in reply to daniele banfi at November 14, 2017 12:30 PM | Reply

https://www.itu.int/rec/R-REC-M.493

As far as I am aware this is free to access and the recommendation can be downloaded in several languages.

This recommendation has been implemented by ETSI standard EN 301 132, which requires the MOB to have a receiver so that acknowledgements are received and acted upon (tests in section 10). All ETSI standards are freely available. This one is at http://www.etsi.org/deliver/etsi_en/303100_303199/303132/01.01.01_60/en_303132v010101p.pdf

Posted by: Wince in reply to Ben at November 15, 2017 5:55 AM | Reply

Thank you, Wince! The ETSI document is particularly interesting, though I remain confused. A DSC receiver seems clearly called for, but then again there is no test procedure given Closed Loop (your own boat or MMSI group only) DSC distress alerts.

I also note that the labeling recommendations reference two distinct types...

Open loop devices shall be marked DSC-MOB-O.
Closed loop devices shall be marked DSC-MOB-C.

...though the types aren't referenced again.

Finally, I found the EU Certification for the ACR AISLink, which is dated October 2017:

https://www.acrartex.com/media/1377534/aislink-mob-red-type-examination-certificate.pdf

It does note that "DSC functionality may vary to comply with National Regulations; the device has only TX-functionality" but that's what I tried to explain above.

Posted by: Ben in reply to Wince at November 15, 2017 10:51 AM | Reply

Hi,

SRT has been developing radio communication devices for a wide range of applications for over 25 years. We have been looking at MOB/PLB's for a little while, and how AIS could be used, but as yet not brought a product to market. This is due to our concern about real world performance due to the physics of radio propagation. Although we have developed an AIS SART.

The new em-trak B400 high powered Class B, and A200 Class A all have a special MOB alert, track and find application. This instantly generates an alert if an MOB/PLB (SART) transmission is received and brings up a radar type display showing the bearing and distance of the most recent received transmission. As a matter of note, the IEC standards for Class A state that a SART transmission must generate an alert and go to the top of the master vessel list.

However we feel that the main issue is one of the physics of radio and how that works when a radio device is attached to a person who is immersed in water - in particularly in regards to AIS.

Leaving aside the issues related to size of device and antennas, the main issue that we have seen is that if such a device is used in rough weather it is likely to be quite unreliable due to waves blocking GPS reception and or AIS transmission. For optimal and reliable performance the GPS and VHF antennas need to be clear of the water and as high as possible. This is of course quite easy to achieve, but then compromises the everyday convenience of the product.

The electronics of an AIS MOB/PLB are very simple since it's just a simple AIS transmitter, who's performance and operation are defined by the relevant specifications. However the challenge for us manufacturers is the physical implementation of the product such that it is low cost and easy to wear whilst on the boat, but also when needed, that it also works reliably and safely and the user's real world performance and functionality - even in rough seas and bad weather.

Its an area we will continue to look at, but remain concerned that the natural laws of physics might win on this one!

Simon

Posted by: Simon - SRT CEO at November 19, 2017 9:39 AM | Reply

Hi,

Reference the DSC debate, this morning I quickly asked our Customer Support team about this and their reply was as follows:

"Reading the DSC standard it’s clear that DSC receivers are optional, and in the AIS standard it is specifically not required. The additional power required to run a receiver will require a larger battery etc., unless you can assume the distress signal will be acknowledged and the MOB can elect to stop transmitting sooner rather than later, then maybe the same size battery could be used. I can see that if you’re in the water receiving an acknowledgement would be a great comfort, but it doesn’t help you to be rescued in anyway. One may prefer to use the available power to transmit for longer."

I hope this is of help.

Rgds

Simon

Posted by: Anonymous at November 20, 2017 5:07 AM | Reply

I'm not sure which DSC standard is being referred to as EN 303 132 states in section 5.1:

"Transmission shall only commence if the channel is not busy (Listen Before Talk). The locating
beacon shall have an integral DSC receiver capable of receiving distress acknowledgements."

So there are two reasons it is necessary to have a DSC receiver - make sure the channel is clear and receive acknowledgements.

I agree there is no such requirement on AIS MOB (as defined in EN 303 098). But I am confused by the statement "it's clear that DSC receivers are optional" as to me the standard (EN 303 132 as listed on the AISLink type approval certificate) is very clear that they are a requirement. I would love to know what I am missing!

Posted by: Wince in reply to Anonymous at November 20, 2017 9:10 AM | Reply

Hi,

Earlier today I posted a quote in relation to the DSC requirements. Our Test & Compliance Manager has pointed out that what I posted was INCORRECT. My apologies for any confusion caused - this is entirely my fault in cutting and pasting in haste from an internal email within our Customer Support Department. I should have checked with the right people in SRT who deal with these matters daily.

The correct position as far as we are concerned is as follows:

According to the global DSC standard ITU-R M.493-14 for both an ‘open loop’ and ‘closed loop’ MOB device using VHF DSC, both a receiver and transceiver is required. The MOB is required to cease transmitting the distress alert when an acknowledgement is received and indicated to the user as described in section 16.6. This is backed up by ETSI EN 303 132 (which is a European Standard) which requires that a receiver and transmitter are required, and made very clear in Figure 1 of the ETSI standard (see below). The fact that ACR has had the AISLink device ‘type approved’ under the relatively new ‘Radio Equipment Directive’ (RED) may be technically OK as the RED requires devices to meet the relevant ‘essential requirements’ of the directive, which isn’t necessarily every last word of any given standard. These essential requirements are listed on the RED certificate and are generic requirements focused very much on the health and safety of the user, electromagnetic compatibility, and the effect on radio spectrum usage. Of the twelve essential requirements listed on the certificate only four are deemed relevant to the AISLink by the notified body, none of which specifically require compliance with any particular standard. However, The type approval certificate states that AISLink is compliant with EN 303 132 v1.1.1 which it is not, if it doesn’t have a receiver. Therefore one assumes that it does have a receiver if this is what is being claimed and has been tested and certified.

Again, my sincere apologies for my error.

Rgds

Simon

Posted by: Simon - SRT CEO at November 20, 2017 1:07 PM | Reply

Simon, the RED certificate notes that the ACR aisLink does not have a DSC receiver (as I quoted above):

"DSC functionality may vary to comply with National Regulations; the device has only TX-functionality"

And if RED is about essential requirements, that makes sense to me. I don't see how unacknowledged 0.5 Watt DSC closed loop calls could cause much trouble, and I believe that the open loop calls allowed in some jurisdictions are a single automatic burst -- no acknowledgement required -- and single manual bursts after that, again no acknowledgement required to end transmission.

I'm no expert on this (or much else ;-), but I do think the DSC MoB routines were designed to avoid a receiver so as to reduce device size and cost.

Posted by: Ben in reply to Simon - SRT CEO at November 20, 2017 1:48 PM | Reply

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